The present invention relates to an earth working device and in particular to a farming implement such as a cultivator or the like.
More specifically, the invention is directed to an improvement in the system for controlling the depth of penetration of earth by working tools on a farming implement and for raising the implement for transportation purposes or the like. The invention is explained with reference to an agricultural tillage implement such as a cultivator. However, it can be used with any other farming implement in which the control of the level or depth of penetration of the earth working tools is of the essence.
Many agricultural implements of the type including tilling shovels are known from prior art. They are usually towed by a tractor and can be divided into two basic groups from the standpoint of the way of securement to a tractor. The first group is more or less fixedly secured to the tractor such that when the tractor reaches an elevated position, the whole implement follows the inclination thus induced. The second group of the towed implement of this type utilizes so-called "floating hitch" wherein the front of the frame of the implement is provided with a pivotal or hinged securement of the towing bar whose opposite end is then secured to the tractor. The latter arrangement is typical by having a number of wheel subassemblies which include a set of front wheels and a set of rear wheels. The advantage of the "floating hitch" is in that the implement more closely follows all irregularities of the surface of a field and thus provides a more uniform depth of penetration of the earth by the tools.
It is one of the prerequisites of farming implements of this type that they be capable of becoming readily convertible from a transportation position, at which the earth working tools are lifted substantially above the ground, to a working position in which the frame of the implement with the tools is lowered such that the tools penetrate the soil to a predetermined depth. It is also important to assure that the operator of the tractor can readily adjust the instant depth of penetration of the soil by the earth working tools secured to the frame of the apparatus, during the operation.
A number of different ways of controlling the depth of penetration by the tools are known from prior art. They operate on hydraulic, mechanical or combined principles and utilize many different ways of obtaining as level an arrangement as possible. It is important not only to achieve proper maintaining of the frame of the implement at a horizontal level (thus securing uniform depth of penetration by the working tools), but also to ensure that the horizontal, levelled arrangement is retained in a fully raised position, in which the wings of an implement are folded into an upright position where virtually any misalignment of the front-rear level of the frame would be visible and unacceptable.
As regards prior art, reference may be had to the following patents utilizing the system of a floating hinge: U.S. Pat. No. 4,083,411 (van der Lely), Canadian Pat. No. 803,220 (Sokolik), and Canadian Pat. No. 727,392 (Telecky).
In Canadian Pat. No. 727,392, a triangular frame is provided with front and rear wheels. The lifting is achieved by an additional or supplementary frame, referred to as "lift frame", which is raised or lowered according to the instant need of the type of working the soil. The arrangement is disadvantageous since it does not allow for convenient levelling of the device in case of a front-rear misalignment or in case of a sideways misalignment. Generally the same disadvantages are encountered in the Sokolik device which also utilizes what amounts in effect to a sub-frame lifted or lowered by a hydraulic arrangement as the need arises. In the van der Lely U.S. Pat. No. 4,083,411, the depth of penetration is in fact controlled by a pilot wheel contacting the ground. A separate hydraulic mechanism is utilized for lifting and lowering the frame of the device from a transport position to an earth working position. The levelling of the frame transversely and longitudinally is cumbersome.
U.S. Pat. No. 2,682,153 issued June 29, 1954 to R. C. Fink, Sr. shows a trench roller having a wheel raising mechanism comprising a front arm and a rear arm linkage mechanism interconnected by a connecting rod to lower or to raise auxiliary wheels designed to ride in a trench. While Fink Sr. attempted to achieve raising and lowering the wheels in like amounts, it only refers to the proportioning of the linkage mechanism and otherwise presents a complex mechanism which, while being probably suitable for the purpose described, would not be accurate enough if used in farming implements.